Brake system with floating piston-main brake cylinder unit with a novel type of MUX control (MUX 2.0) with at least one outlet valve, and method for regulating pressure

A method of testing tightness and mobility of a floating piston of a main brake cylinder of a brake system with

• the main brake cylinder and the floating piston arranged in the main cylinder, wherein the floating piston is configured to hermetically separate first and second pressure chambers from one another, wherein the first pressure chamber is hydraulically connected to a first brake circuit and the second pressure chamber is hydraulically connected to a second brake circuit,
• a pressure medium reservoir under atmospheric pressure,
• wheel brakes,
• an electrically controllable pressure supply device configured for pressure build-up and pressure reduction in the wheel brakes,
• a valve block with a currentless open inlet valve/switching valve for each respective wheel brake, and with at least one outlet valve,
• wherein each respective wheel brake is configured to be hydraulically connected to a pressure chamber of the main brake cylinder via a respective one of the switching valves, and is also configured to be hydraulically connected to the pressure supply device directly or via one or more isolating valves,
• wherein each brake circuit is configured to be hydraulically connected to the pressure supply device by means of at least one controllable valve,
• wherein the main brake cylinder has a radially extending channel in its cylinder wall, which opens out in the first pressure chamber, wherein a mouth opening of the channel is closed by the floating piston when the floating piston as is displaced from its normal position by an amount at least equal to a diameter of the mouth, wherein the channel is in hydraulic communication with a pressure chamber of the pressure supply device, wherein a mechanical stop is arranged in the main brake cylinder and a spring exerts a force on the floating piston in a direction of the stop, and wherein the floating piston is in its normal position when it rests against the stop, the method including:
• a. building up a pressure in the first and second pressure chambers via the pressure generating unit, and switching valves such that a pressure in the second pressure chamber is greater than a pressure in the first pressure chamber, and moving the floating piston to close the channel;
• b. generating a test path profile of the floating piston and/or a pressure volume profile over time for one of the first or second pressure chambers of the main brake cylinder by means of the pressure supply device, to result in a pressure profile;
• and
• c. comparing and evaluating, based on a signal of a pressure transducer, the pressure profile with a target value profile with the inlet/switching valves associated with the wheel brakes open.

A method of testing tightness and mobility of the floating piston of a main brake cylinder of a brake system with

• the main brake cylinder and the floating piston arranged in the main cylinder, wherein the floating piston is configured to hermetically separate first and second pressure chambers from one another, wherein the first pressure chamber is hydraulically connected to a first brake circuit and the second pressure chamber is hydraulically connected to a second brake circuit,
• a pressure medium reservoir under atmospheric pressure,
• wheel brakes,
• an electrically controllable pressure supply device configured for pressure build-up and pressure reduction in the wheel brakes,
• a valve block with a currentless open inlet valve/switching valve for each respective wheel brake, and with at least one outlet valve,
• wherein each respective wheel brake is configured to be hydraulically connected to a pressure chamber of the main brake cylinder via a respective one of the switching valves, and is also configured to be hydraulically connected to the pressure supply device directly or via one or more isolating valves,
• wherein each brake circuit is configured to be hydraulically connected to the pressure supply device by means of at least one controllable valve,
• wherein the method comprises:
• a) storing a pressure in the second brake circuit by closing the inlet/switching valves associated with the second brake circuit during a parking stop, when a vehicle incorporating the brake system is stationary;
• b) following the storing, reducing a pressure in the first brake circuit to 0 to 1 bar by means of the pressure supply device;
• c) following the reducing the pressure in the first brake circuit, blocking the pressure supply device unit in such a way that a piston movement of a piston of the pressure supply device no longer takes place, wherein the control device closes one of the isolating valves disposed between the pressure supply device and the second brake circuit;
• d) opening the inlet/switching valves associated with the second brake circuit, following the blocking the pressure supply device, whereby the floating piston moves on account of pressure on its rear side, and as a result, building up the pressure in the first brake circuit until a pressure equilibrium is established between the first and second brake circuits;
• and
• e) measuring the pressure in one of the first or second brake circuits by means of a pressure sensor in one of the first or second brake circuits, and evaluating a resulting pressure profile.